AW: Propagate default route when BGP session is up

22 Aug 2017

      Hi Robert,

some time ago we had the same question which brought us to the following solution:
we wrote a simple shell script which checks if the bgp session is up.
If so, the router runs bird and propagates the default route.
If the connection is down the router disables bgp and the other router becomes the master (which hopefully still has the active and correct bgp session).

Greeting Sascha
...
-----Ursprüngliche Nachricht-----
Von: Bird-users [mailto:bird-users-bounces@network.cz] Im Auftrag von
Robert Sander
Gesendet: Freitag, 18. August 2017 16:05
An: Bird Users
Betreff: Propagate default route when BGP session is up
Hi,
how do I propagate a default route into OSPF when a specific BGP session is
up and not propagate it when it is down?
Currently I have these config snippets:
protocol static static_default {
  preference 10;
  route 0.0.0.0/0 unreachable;
}
function export_ospf() {
  if source = RTS_BGP then {
    return false;
  }
  if proto = "static_bgp" then {
    return false;
  }
  return true;
}
protocol ospf {
  rfc1583compat on;
  import all;
  export filter {
    if export_ospf() then accept;
    reject;
  };
  area 0 {
    interface "ospf" {
      cost 10;
      hello 10;
      retransmit 5;
      dead 45;
    };
  };
}
protocol bgp ispa1 {
  description "ISP A1";
  import all;
  export filter {
    if proto = "static_bgp" then accept;
    reject;
  };
  local 1.2.3.6 as 1;
  neighbor 1.2.3.5 as 2;
  password "xyz";
}
I can manually "birdc disable static_default" to not propagate the default
route but how can this be automated when the BGP session to
ispa1 is down?
Regards
--
Robert Sander
Heinlein Support GmbH
Schwedter Str. 8/9b, 10119 Berlin
http://www.heinlein-support.de
Tel: 030 / 405051-43
Fax: 030 / 405051-19
Zwangsangaben lt. §35a GmbHG:
HRB 93818 B / Amtsgericht Berlin-Charlottenburg,
Geschäftsführer: Peer Heinlein -- Sitz: Berlin

AW: Propagate default route when BGP session is up

Rohrmann Sascha